Conventionally, a circuit board, such as a printed circuit board, has been commonly and widely used in order to compactly incorporate electronic parts into electronic equipment. The printed circuit board contains a copper foil, which is adhered onto a laminate board, and is etched along an electronic circuit pattern. The printed circuit board is advantageous in terms of a cost, but it is difficult to pack electronic parts with high density.
Meanwhile, there is a rapid trend for making more minute and more laminated layers of an electronic circuit of a circuit board, and for realizing a higher density packaging of electronic parts, corresponding to the demands for electronic equipment having a smaller size, higher performances, and lower price. Therefore, a study of a build-up multilayer circuit board for use as a circuit board has been actively conducted.
As for the build-up multilayer circuit board, for example, disclosed is a build-up multilayer substrate, in which a substrate layer formed of an insulating material (an organic material layer, such as of an epoxy resin) is sequentially laminated on both surfaces of a core material serving as a base (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2004-158671).
In the disclosed method, formation of multiple layers is realized by sequentially forming (building up) a substrate layer, such as an insulating material (an organic material layer, such as of an epoxy resin), which has an electroconductive pattern formed of a copper foil, such as an electrolysis copper foil, on the core material.
The disclosed method however has problems that a production process is extremely long, and a production cost is high.
Therefore, disclosed is a production method of a package substrate for a semiconductor device, in which a plurality of thermoplastic resin layers are formed, electroconductive vias are formed in all of the thermoplastic resin layers, or the all of the thermoplastic resin layer excluding the outermost layer, where the vias penetrate through in the thickness direction of the thermoplastic resin layer, a metal layer for constituting an electroconductive pattern is provided on a surface of at least one thermoplastic resin layer, the plurality of the thermoplastic resin layer are laminated, and are collectively heated and pressed to fixed to each other to integrate (see, for example, JP-A No. 2006-073622).
The disclosed method however has a problem that a thickness of an obtained package substrate is not uniform because of surface irregularities of the plurality of the thermoplastic resin layers formed when the plurality of the thermoplastic resin layer are laminated and are collectively heated and pressed to fix to each other to integrate.
Accordingly, there is currently a need for a circuit board, which can be produced with a short production process, and has a uniform thickness, a production process thereof, and electronic equipment containing the circuit board.